The invention relates to a nozzle assembly for a fuel injector for injecting fuel into the combustion chamber of an internal combustion engine. Furthermore, the invention relates to a fuel injector having a nozzle assembly of this type.
Laid-open specification DE 10 2011 076 665 A1 has disclosed a nozzle assembly for a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, which nozzle assembly comprises a nozzle needle which is received in a high pressure bore of a nozzle body such that it can perform stroke movements in order to open and close at least one injection opening. The nozzle needle is loaded in the closing direction by the spring force of a closing spring which is supported on one side on a body component of the fuel injector and on the other side on a throttle bore body which surrounds the nozzle needle in regions. The throttle bore body in turn is supported on a shoulder of the nozzle needle. At least one throttle bore is configured in the throttle bore body, which throttle bore serves as a closing throttle and divides the high pressure bore into a first and a second part region. A hydraulic pressure p1 prevails in the first part region which lies upstream in the flow direction of the fuel in relation to the second part region, and a hydraulic pressure p2 prevails in the second part region, which hydraulic pressure p2 is smaller than p1, since the fuel has to pass the throttle bore, in order to pass from the first part region into the second part region during an injection operation. At the same time, the throttle bore body which surrounds the nozzle needle in regions has a hydraulically active area A1 which delimits the first part region and is larger than a hydraulically active area A2 which delimits the second part region. Said measures, in each case on their own or in combination, lead to a hydraulic pressure force which acts in the closing direction in addition to the spring force of the closing spring and accelerates the closing operation being generated on the throttle bore body and therefore on the nozzle needle.
The throttle bore body from DE 10 2011 076 665 A1 which surrounds the nozzle needle is pressed against a shoulder of the nozzle needle via the spring force of the closing spring and the additionally acting hydraulic pressure force, with the result that there is a high sealing action in the contact region. Bypass leakage paths which nullify the effect of the at least one throttle bore again at least partially can be produced, however, in the region of the guide of the throttle bore body within the high pressure bore.